The conventional reed switch includes a glass tube having two low magnetic hysteresis ferrous metal reeds. The metal reeds are consisted of 80% nickel and 20% iron, whose end portions are separated by a small gap when the switch is open, whose contact points are plated with a hard metal layer and are usually made of rhodium and ruthenium. The hard metal layer increases service life of the reed switch. The glass tube is filled with nitrogen or equal noble gas usually. The glass tube is vacuumed for increasing performance of switch voltage.
The metal reeds can be actuated to make a contact by using an external magnetic field and the loop of the reed switch is normally in close state. When the external magnetic field is removed, a spring returns the reed back to its original position and the loop of the reed switch is once again an open circuit.
To compare with the conventional reed switch, the micro reed switch is deposited with precious metal (rhodium, rubidium or ruthenium), whose structure has high melting and thermostability material, which can receive high current to increase device character. For example, Min Tang, Yong Hean Lee, Rakesh Kumar, Member, IEEE, Ravi Shankar, Olivier Le Néel and Giuseppe Noviello disclose a MEMS microreed switch with one reed embedded in Journal of Microelectromechanical Systems, vol. 20, No. 6, December 2011, which consists of two Ni80Fe20 magnetic plates as microreeds.
However, the micro reed switch is fabricated by semiconductor fabrication or micro-electromechanical fabrication, which has high manufacture cost, and current carrying capacity is only 0.1 milliamperes that does not accord to the requirement (at least 50 milliamperes) of the conventional reed switch. Even all engineers know the fault; they seem to have no acceptable and easy solution to solve the problem.